so we incresed the debian package name from libosmoctrl0 to libosmoctrl1 at the time of the 0.10.0 release. However, the library name is still libosmoctrl.0, most likely because LIBVERSION=1:0:1, i.e. the "age" is set to 1, meaning the library supports both the "0" as well as the "1" API version?

We have two choices, AFAICT:

return to "libosmoctrl0" package name (and the dependencies)

do whatever it takes to produce libosmoctrl.so.1 (probably remove the "age")?

I don't know enough about how debian packaging deals with / interacts with libversions. From the library point of view it makes sense to have the 1:0:1 i.e. API 0 + 1 compatible. But how does the package manager deal with that?

keith: Also, why is it not simply replacing libosmoctrl0 with libosmoctrl1? do you have any packages installed depending on libosmoctrl0?

keith: Also, why is it not simply replacing libosmoctrl0 with libosmoctrl1? do you have any packages installed depending on libosmoctrl0?

Well, yes, pre-ugrading, at least osmocom-nitb depends on libosmoctrl0, of course.It is true that I added the newer libosmocore packages to my repo and attempted upgrade of libosmocore before also adding the updated osmocom-nitb package to the repo, so maybe having the updated osmocom-nitb package depending on libosmoctrl1 would allow dpkg to replace libosmoctrl0 with libosmoctrl1.

I don't have enough dpkg-foo to know. I'll roll back to the previous package state and complete the repo and test..

After some more googling, it seems that asking for a libtool-style current[:revision[:age]] style specification is the sanest thing to do. The field could then be called version-info, the name in libtool. Perhaps library-version-info would make it even less ambiguous.
On linux, current:revision:age gets translated into version number major.age.revision, where major=current-age, reflecting the fact that ABIs can be backwards compatible. And then the SONAME is libfoo.so.major.

I'll update the wiki page and update the debian packages accordingly following this explanation.